SERVICE_DRY ICE BLASTING

1. Service
DRY ICE BLASTING
Generalities, methods,
instruments
and on site experiences
PPT2013.01.01.23EN
www.nidec-asi.com

2. Periodic Maintenance Program
4.000 hrs

Mechanical
diagnostics
(detecting vibrations
and temperatures)
8.000 hrs

Electrical & mechanical
diagnostics (detecting
also electrical
parameters: partial
discharges, insulation
res., P.I….)
20.000 hrs

Electrical &
mechanical
diagnostics + partial
disassembling to
inspect main
components
40.000 hrs

Electrical &
mechanical
diagnostics +
General
Overhauling
Keeping the Electrical Motors cleaned during the whole life cycle is a key priority because it
permits to:
 reduce risk of failure
 maintain performances
 increase reliability
PPT2013.01.01.23EN
www.nidec-asi.com
2

3. Risk for motors in critical environments
Each ambient condition is related to a risk factor
Ambient conditions
Contaminants
grease & oil
aging rate
temperature
dust & dirt
efficiency
Risk of failures
Risk factor
sand
PPT2013.01.01.23EN
www.nidec-asi.com
3

4. Dry Ice Blasting Principles
Impact
Upon impact – generated by the speed and mass
of the CryoPellets – kinetic energy is transformed
into an abrasive cleaning force.
Explosive sublimation
The dry ice pellets temperature is around -79º C;
Fast transfer of heat from the pellets to the warm
surface to be cleaned causes instant sublimation
to gas phase; Volume increase (500 times) ⇒
contaminants blasting.
Thermoshock
Sudden local cooling + differences in shrinkage
rate ⇒ tension between contamination & substrate
⇒ contamination breaks free from surface.
Glass transition point
Once the temperature drops below the glass
transition point, the material becomes brittle.
PPT2013.01.01.23EN
www.nidec-asi.com
4

5. Dry Ice Blasting Process
Dry Ice Pellets are made by taking liquid carbon dioxide
(CO2) from a pressurized storage tank and expanding it
at ambient pressure to produce snow. The snow is then
compressed through a die to make hard pellets.
Impact + Explosive sublimation + Thermoshock + Glass transition point
= CLEAN SURFACE
PPT2013.01.01.23EN
www.nidec-asi.com
5

6. Dry Ice Blasting Tools and Instruments
Pellet Storage
Ready to use
Mobile Air Compressor
7380 lt / min
10 bar
Air Preparation Machine
Includes: water separator, pre-filter, freeze
drieer, oilfilter and a thermostatic controlled
aftercooler
AIR
OEM’s
indications
Pellets Storage Container
Outer dimensions (lxwxh): 996 x 926 x 810 mm
Capacity: 262 litres (approx. 206 kg pellets)
Dry Ice Blaster
Compressed air
ICE
Blasting Hose
Guns & Noozles
PPT2013.01.01.23EN
www.nidec-asi.com
6

7. Cleaning Electric Motors
Dry Ice Blasting effectively removes the contaminants from all parts
of the motor – stator (windings), rotor (internal fans, cage), air ducts
(heat exchanger, external fans) and other components (bearings,
shields, inner cups, terminal boxes)..
Benefits of Ice Blasting
Cleaning Method Comparison
Dry Ice Blasting
Issue
Traditional
very low
Equipment Downtime
high
low
Hazardous Waste
medium
low
Labour Hours
medium / high
high
Quality of Cleaning
medium / low
very low
Potential Equipment
Damage
medium
high
Safety
medium
low
Cost
medium / high
PPT2013.01.01.23EN
www.nidec-asi.com
7

8. On site experience




Contaminants
oil, dust
Timing
2 days for complete stator, rotor and components dry ice
cleaning vs 4 days as per standard procedure (solvents
cleaning + oven heating);
Consumables
400kg dry ice used;
Improvements
better insulation measured after stator (from 100MΏ to 4.7 GΏ )
& rotor coils cleaning
Tan – delta: close to new manufactured stators
eliminating dangerous contaminants (oil film) results into:
- extended operating life of insulation (=
generator)
- improved measurements detected of tan-delta /
partial discharges
On site General Overhauling of 11kV – 13.569 kVA – 30 tons generator
PPT2013.01.01.23EN
www.nidec-asi.com
8

9. On site experience
Stator coils before dry ice cleaning
The coils were completely covered
by a oil film going to affect the
insulating properties of the stator.
after dry ice cleaning
The main electrical parameters
measured after the Ice Blasting
Cleaning improved significantly
Insulating resistance: from 100MΏ to 4.7 GΏ
Tan – delta: close to new manufactured stators
PPT2013.01.01.23EN
www.nidec-asi.com
9

10. On site experience
Ice Blasting Cleaning of single generator components
Ice Blasting Cleaning of single generator components
Stator
PPT2013.01.01.23EN
Shields
www.nidec-asi.com
10

11. On site experience
Ice Blasting Cleaning of single generator components
Ice Blasting Cleaning of single generator components
Rotor
before
after
PPT2013.01.01.23EN
www.nidec-asi.com
11

12. Conclusions

Dry Ice Blasting is a powerful and reliable cleaning
technique

Main benefits:
–
–
Reduced labour hours
–
High quality of cleaning with no damages on
equipment
–
Low cost
–
PPT2013.01.01.23EN
Very low Equipment Downtime
Safe to apply and pollution free
www.nidec-asi.com
12